Thermionic transmitter and receiver



Nov. 1, 1932. SC TEL 1,885,770

THERMIONIC TRANSMITTER AND RECEIVER Filed Sept. 20, 1926 v 2Sheets-Sheet 1 Z I I: 97

Nov. 1, 1932. G, SCHOTEL 1,885,770

THERMIONIC TRANSMITTER AND RECEIVER Filed Sept. 20, 1926 v 2Sheets-Sheet 2- Z WHkw jib 2 126 Patented Nov. 1, 1932 unites ems insaneGERRIT SCI-HOTEL, OF THE HAGUE, NETHERLANDS THERMIONIC TRANSMITTERRECEIVER Application filed September 20, 1926, Serial No. 136,652, andin the Netherlands September 25, 1925.

The invention relates to improvements in or relating to thermionictransmitters and receivers more particularly for short waves.

The improvements accordingto the preslfent inve'ntionwith regard to thethermionic transmitters more particularly for short waves consist inthat two or more circuits are coupled very tightly with each other, e.g.,

by means of a common coil with tapping 10 points and are inserted in thecircuit of a discharge tube and by suitable'means the higher: or one ofthe higherresonant frequencies is brought into action. Hereby theelficiency may be regulated by alteration of the winding-ratio of thecoupling coil or coupling coils. With the aidof an adjustable coilconnected'to the regulating electrode, which forms with the capacity ofthe H tube an oscillating circuit, the invention in- 'cludes theregulating of this circuit to a frequency which is higher than theoperating frequency.

l/Vith regard to thermionic receivers the invention consists in theimprovement whereby two or more circuits tightly coupled with each otherare inserted in the grid circuit of a discharge tube and the circuits soadjusted that the higher or one of the'higher resonant oscillationfrequencies is the same as the wave-length to be received, orapproximately so in case of beat reception, Hereby the efficiency ofreception can, when necessary under application of known means forre-tuning be regulated by alteration of the winding-ratio of thecoupling coil or of the coupling coils.

Other characteristics of the invention are that in the case of atransmitter the self- 40 pling coils between the tube and the antennafying purposes; and

, induction of the coupling coil or of'the cou Figure 3 shows a diagramof connections inwhich the aerial has been replaced by an adjustablecondenser and a resistance;

Figure 4c is a dia rammatic representation explaining the conditionsofoperation of the electron tube; 1

Figure 5 shows the connections for using the present invention forreceiving purposes;

Figure 6 shows the connections for ampli- Figure 7 is a diagram of apush-pull circuit.

Referring to Figure '1, the electron tube 1 V has a filament 2, a grid 3andan anode 1. The tube anode circuit may be fed in parallel,- asillustrated. However, this method of feeding anode current to the tubeis optional, and any other usual method may be used if desired." With aparallel feed, the blocking condenser 5 is" provided for preventing thedirect current of the anode battery or genera tor from taking the wrongpath through the coil 6. The latter has two adjustable tapping points,one of which is used for the anode circuit 7 and the other for theaerial 8.

The grid circuit comprises 'anadjustable self-induction coil 9 connectedinseries with agrid resistance 10 bridged by a condenser 11. 'Thecapacity present in the electron tube provides a coupling between theanode cir cuit and the grid circuit, whereby according to a knownprinciple electric oscillations are continuously produced in the saidcircuits. By suitablyselecting. the elements arranged in Figure 1between the grid and the filament ina manner to be more fully describedthe electron tube will oscillate with a considerablyhigher frequency.than that produced if these elements were selected otherwise. The systemconsisting of the coupled circuits 2-- 3 4 -56 and 68aerial"earth isresonant to'two frequencies difieringconsiderably 7 from one anotherowing to their very tight coupling. Out of these frequencies it is pos-ysible for'example to select the'highest (apart from the action of thecoupling withf'the grid circuit whereby strictly speaking there is thepossibility ofmore than two frequencies with the present connections)byselecting the elements of the grid circuit so that the internalcapacity coupling of the electron tube produces a grid tension havingthe correct phase and amplitude, with the result that the oscillationsof the highest frequency (or if necessary the intermediate frequency, inthe case of more than two possible frequencies) may continue. In thecase of Figure 1 the correct phase above mentioned is attained byselecting the inductance of the coil 9 so as to make the naturalfrequency of the circuit consistingof this coil and the tube capacityslightly higher than the frequency of the oscillations generated, Anytendency to oscillate at a frequency considerably lower than that towhich the grid circuit is tuned will not be sustained by the action ofthe grid-filament circuit because the lowinductance of the coil 9 willform a short circuit for'the lower frequency. Figure 1 is of coursegiven as an example, since a number of modifications may be made in theconnections without departing from the fundamental principle of theinvention.

Referring to Figure 4, illustrating a diagram with two circuits coupledto one another, the operation of the tube is as follows,

knowing that C; is the internal tube capacity between anode and filamentterminals of the electron tube; the influence of the grid coil beingalso taken into account; L the induc-' tance at no loadof a transformerwithout losses and magnetic leakage, that is to say" having a 100%efficiency; Z an inductance; C a capacity and R a resistance. The valuec of the last two elements is given when they erally however thecoupling of the grid circuit with theother circuits is, if theadjustments are right, loose, so that the larger natural frequencies arenot far apart.

"Figure 4 is a. diagrammatic representation of the connections ofFigure 1. The block condenser 5 is omitted and the ratio oftransformation u (i. e. the turn ratio from primary to secondary) of thetransformer 6 is assumed to be u=1z 1. This transformer is thereforereplaced by an inductance L representing the no-load inductance. j X

As a rule Lis many times greater than Z and C many times greater than 0The resonant frequencies of the system are approximately:

1 '1 21 /10, 2 21r,/ Should. the winding ratio of the transformer be uinsteadof unity, then Z and R are first to be multiplied by a and C tobe divided thereby.

In the present invention frequency F is used, care being taken that F iskept in check. r

The transformer may be omitted when the winding ratio is u=1. Thisextremecase is shown in Figure 2, in which the aerial is directlyconnected to the coil 12.

Figure 3 illustrates the general case, in which the winding ratio u ofthe transformer varies from, unity, and there is a certain amount ofmagneticleakage which will appear as self-induction in the. circuit fromwhich the energy is available.

'Thecapacity of the aerial is replaced in this case bya variablecondenser 13. Also a variable self-induction may be connected in placeof the aerial, or the transformer "may be short-circuited (extreme caseof the con denser connection with infinite capacity according-to Figure3).

The wave-length may be altered firstly by F1 /u lO, 21m, 10, which meansthat the Wave-length varies proportionally to the ratio oftransformation.

Secondly, the impedance of the circuits connected to the tube is ofgreat importance. This impedance is under the same conditions asmentioned above for the frequency, defined by the formula and mustbeadaptedto the impedance of the electron tube, in order to obtain asufficient radiation and a good efficiency. If the conditions mentioned,namely that the transformer has no leakage nor losses and no distributedcapaclty and C u C are not the resulting inductance (Z in the formulafor F so that the inductance of the antenna coil (12, Figure 1) maybereduced or this coil omitted. By building suitablecoils the losses inthe transformer in general will be very small.

Particularly .forshort waves, whereu 1, the. condition C u C will be as.a rule fulfilled. 1

Thedeviations from the theoretical case will have no other effect thanto make it dif lengths used.

fieult to calculate the correct winding-ratio in advance. On the otherhand it is easy to determine experimentally the positions of theadjustable contacts or winding-ratio,-

drop and thus detriinentally affect the opera tion of the dischargetube. The present method makes it possible to alter Z 111 -013- erationwith the value of It and to ad ust the wave-length with the aid of theratio of transformation. 'lVhen applying the present invention on theabove lines, there is no difficulty in obtaining a good efficiency evenin case very short waves are used, and also when the aerial, whateverits dimensions, is con nected by direct coupling to the anode of thetube. As the aerial capacity does not appear in tne formula for thewave-length the present method has moreover the advantage that theradiated wave-length can be easier kept constant. Usually an aerial,when emitting waves having a wavelength several time shorter than itsnatural wave length has a' high total resistance which varies onlyslightly with the different short wave- Thus the ratio of the anodetransformer (coil 6 in Figure 1) must be approximately proportional tothe wavelength, in order to obtain the same good results on difierentwave-lengths.

In Figure 5 the aerial is connected directly to the grid circuit of thetube 1 with the aid of the coil 14. By suitably operating the contactsand 16 or any other known regulating means, the higher or one of thehigher resonant frequencies of-the coupled circuits is tuned to, or incase of beat recept1on, ap-' proximately tuned to the wave-length to berecelved. ble in the anode circuit by suitable means.

The method of tuning the system comprising the aerial circuit givesanother advantage over the generally used method for reception of shortwaves, where the aerial circuit is not tuned. 7

An adjustable inductance 17 is inserted in the anode circuit in order toobtain the proper impedance in the said circuit for the wavelength whichis to be received.

In the receiving circuits of Figures 5 and 6 the resulting capacitybetween grid vand filament terminals corresponds to the capacity C(mentioned above).

A receiving arrangement of the same kind is illustrated in Figure 6 foramplified reception in which the signals received are amcor The si 'nalsma be rendered audi-,

plifie'd by the tube 1 and forwarded to the grid of the following tube.In this case the higherv or one of the higher resonant frequencies alsoof the intermediate circuits is regulatedto the wavelength to bereceived. The capacity of one of the tightly coupled circuits maybelarge, which is also an'advantage when receiving short waves.

All systems of connection used in this method may be carried out as'push-pull connection if the aerial has only an inductive coupling withthe tube. There is, however, a case in which a direct coupling of aerialand tube circuits is possible under use of pushpull connection. For thatpurpose (see Fig; 7) two vertical aerials 8 and 8a are located at adistance apart of half the wavelength wanted and are directly coupled tothe tubes 1 and 1a; The middle of the anode coils 6,-

6a is earthed, the distances between the lower ends of the aerials andthe earth connection being equal; Anode current is supplied by asuitablesource of current feeding each of the anodes through a hi h frequencychoke coil.

The anodes of both tubes used are connection, so'that a diagram ofconnections is ed composed of Figure l and its image. The currents inthe'two' aerials willthen have a phase difference ,of180., which resultsin a directionaleifect. iv

' The invention is not limited to the use of connections in which theanode circuit and the grids circuit are coupled to each other only bymeans of the'anode grid capacity-of thedischarg-e tube. I coupling thesecircuits outside the tube may 1 without departing from the invenbe usedtion.

What I claim is I 1. The combination with 'a'thermionicdischarge tubehavingan input circuit and an output circuit, of a high frequencynetwork stituted by a plurality of tightly coupled circuits connected inone of said tube'circuits so to form a network with a plurality of res 1lie frequencies and means for bringing one or the higher frequenciesinto action.

. $4. lhe combination with a ther1nionicdischarge tube having an inputcircuit and an output circuit, efa high frequency network constitut d aplurality oftightly coupled circuits connected in one of said tubecircuits so as to form a network with a plurality of. resonancefrequencies lying in the range of radio frequencies, and means in theother circuit for bringing o-ne'of, the higher frequenciesinto action.

The combination with a thermionic disonance frequencies lying in therange of nected at equal distances from the earth con- Any known meansfor. 7

charge tube having an input circuit and put circuit so as to form anetwork with a plurality of resonance frequencies lying in the range ofradio frequencies and means in the input circuit for causing the tube tooscillate to one of the higher frequencies.

a. The combination witha thermionic discharge tube having an inputcircuit and an output circuit, of a high frequency network constitutedby a plurality of tightly coupled circuits connected in the outputcircuit and including an antenna, said network having a plurality ofresonance frequencies lylng 1n the range of radlo frequencies, and means1n the input circuit for causing the tube to oscillate at one of thehigher of said frequencies. 5. The method of regulating the ratio ofdirect current lnput to alternating current output in a thermionictransmitter having its output circuit tightly coupled to 'the radiatingcircuit through a transformer to form a high frequency network with aplurality of resonance frequencies of radio frequency at one of whichthe thermionic transmltter OSClllates, which comprises changing thewinding ratio of the transformer while malntalning the resonantfrequency of the coupled circuits and feed-back coupling constant.

6. The combination with a thermionic discharge tube having an inputcircuit and an output circuit, of a transformer, a plurality of circuitstightly coupled through said transformer and connected in one of saidtube circuits forming a high frequency net work resonant to a pluralityof radio frequencies, and means for varying the winding ratio of saidtransformer while maintaining one of the frequencies to which saidnetwork resonant substantially constant.

' 7. lhe combination with a thermionic tube, of an output circuittherefor comprising a high frequency network constituted by a pluralityof tightly coupled circuits, so as to form a network with a plurality ofresonance frequencies lying in the range of radio frequencies, and acontrol circuit therefor influenced by the output circuit to cause thetube to oscillate to one of said frequencies, said control circuit beingadjusted to cause the tube to oscillate at one of the higher of saidfrequencies.

8. In combination, a thermionic discharge tube having an input and anoutput circuit, one of said circuits being tightly coupled to a thirdcircuit by means of a common coil to form a high frequency network witha plurality of resonance frequencies of radio frequency at one of whichthe thermionic tube oscillates, and a control coil in the other tubecircuit for determining the frequency to which the tube is to respond,said third circuit being resonant to a lower frequency than the saidinput circult.

' In testimony whereof I hereunto aflix my signature. 7

, GERRIT SCHOTEL.

